Liquid storage tank and seal mechanism



Feb. 20, 1951 1.. A. WILKIN 2,542,444

LIQUID STORAGE TANK AND SEAL MECHANISM Fil ed Jan. 29, 1948 2Sheets-Sheet l INVENTOR.

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Feb. 20, 1951 L. A. WILKiN 2,542,444

LIQUID STORAGE TANK AND SEAL MECHANISM Filed Jan. 29, 1948 2Sheets-Sheet 2 fl F 15 \4 12 p- T1 I 1/ ,E'Q F.

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Patented Feb. 20, 1951 LIQUID STORAGE TANK AND SEAL MECHANISM LesterAnderson signer to Graver Wilkin, East Chicago, 11]., as-

Tank 8; Mfg. 00., Inc., a cor poration of Delaware Application January29, 1948, Serial No. 5,012 4 China. (Cl. 220-26) This invention relatesto storage tanks m1- volatile liquids such as petroleum, gasoline andthe- .like. The invention relates particularly to socalled floatingroofs for such tanks, and to improved peripheral seals for such floatingroofs.

The improvement resides in the fact that the seals according to thisinvention have a plu rality of important and advantageous features,constituting a more efflicient and economical combination thanpreviously known. Each of the seals previously known and used had someof these features, but none had all of them. The most important featuresof the seals and their accessories, according to this invention, arethat they insure efficient and economical sealing action between thefloating roofs and the tank; they are allowed and forced to stay closeto the tank shell; they have predetermined, substantially horizontalmovements relative to the floating roof they are eiliciently andeconomically protected from corrosion; they are readily accessible forinspection and maintenance; they occupy a minimum of space; their entireconstruction and arrangement is economical and dependable; and they arefreely adaptable to a great variety of floating roofs, for differenttypes of volatile liquids. Details of these and other features will bestated in the description which follows.

In the drawing, Fig. 1 shows a tank and floating roof equipped withimproved seal mechanisms according to this invention; the structurebeing shown in central, vertical section through the tank. Fig. 2 is apartial plan view of the structure shown in Fig. 1. Fig. 3 is anenlarged detail from Fig. 1, showing important parts of the sealmechanisms. Fig. 4 shows another detail,

the view being taken in the direction indicated by the lines 4-4 in Fig.2. Fig. 5 is a geometrical diagram of the device according to Fig. 3.

I provide a storage tank I for the volatile liquid or so-called productII. A floating roof l2 rests on the surface I 3 of said product; it issomewhat smaller than the tank, so that a narrow peripheral space isleft around the floating roof II. It is pertinent to state that tanksand roofs as contemplated herein generally range from about 20 ft. toabout 200 ft. in diameter and from about 30 to about 50 ft. in height.The peripheral space around the floating roof is made as narrow aspossible, generally about 6 inches in width, in order to minimize thebulk and cost of the sealing mechanism required to prevent the loss ofvaluable vapors.

In the embodiment of Fig. l the sealing ap- 2 paratus comprises asubstantially cylindrical seal ring l4, contacting the inside of theside wall or shell ii of the tank In in the approximate region oppositethe floating roof [2, and extending from above to below the liquid level13. A seal fabric It connects an upper part of the seal ring I with anupper part of the floating roof II; the seal fabric being clamped tosaid upper, parts by suitable clamping devices I! and I8 respectively.

The seal ring it can be made from corrosionresistant metals such asgalvanized or stainless steel or aluminum and the seal fabric l6 from aflexible, vapor-tight and water-tight material such as rubberized cloth,glass fibre, asbestos or the like. In tanks as contemplated herein ametal seal ring I4 is referably made from a plurality of metal sealshoes i i-A, "-3 etc,., combined into a ring by suitable joints (notshown). The reason for such a plurality of shoes is that shipment andinstallation would be diflicult if the seal ring consisted of fewer andproportionally longer shoes, or of a single shoe; this is true even withrelatively small tanks having a diameter such as 30 or 40 ft.

The joints as well as the seal shoes themselves must have sufficientflexibility to insure intimate contact between the inside of the shelll5 and the outside of the seal ring I4, in order to keep the escape ofvapors at an absolute minimum, while allowing substantially unobstructedupward and downward travel of the roof and seal. Such travel must beallowed in spite of unavoidable irregularities of the tank shell I5,horizontal movements of the roof l2, the effect of wind,

rain, snow, ice, sunshine, heat, and various: other influences. At thesame time, the seal ring ll must have suiiicient rigidity to allowsupport thereof from widely spaced points on the floating roof ii, inthe interest of economy; it being understood that generally, each shoemust be supported from at least one supporting mechanism l9, and thatthese mechanisms are important cost elements. Such rigidity is alsorequired because otherwise the seal ring could be distorted and damaged,upon vertical movements thereof along a shell IS with iceadheringthereto and in other contingencies which are hard to avoid.

A substantially cylindrical metal seal ring ll fulfills each of theseconflicting requirements of flexibility and rigidity to a suflicientdegree, if the metal of the seal shoes is properly selected. Thepreferred metal thickness for such a shoe is in the approximate range ofto $4; inch; the actual selection depending on the type of metal used,the diameter of the tank and roof, and

other factors. Flexibility is mainly requir in a horizontal plane whilerigidity ismainlv required along the vertical, cylindrical surface ofthe shoe. With metal thicknesses as specified these aims are generallyachieved. Again, a metal shoe of such thickness can have considerablelength between its joints or ends; thereby allowing considerable spacingbetween the points of support. This spacing of supports, with onesupport per shoe, can be in the approximate range of 10 to-15 ft. alongthe periphery of the tank or floating roof.

The seal supporting means additionally serves to guide the seal, keepingall relative movements between the seal ring and the floating-roof in ahorizontal plane. I have found such horizontal movements to be desirablefor a number of reasons, particularly because non-horizontal movementsbetween these parts tend to produce local distortion of the seal ring,imperfect sealing contact with the shell, and difficulties'with the sealloading mechanisms.

It is known that such a seal" ring may tend to move inwardly away fromthe tank shell, at some points, if it is not urged outwardly against theshell at closely spaced points; specifically, at points which are spacednot more than about- 3 to 5 feet from one another if the seal ring isconstructed and dimensioned as indicated above. Again, there is someobvious conflict present, since the permissible spacing of seal supportsexceeds that of the positions for outward loading of the seal. However,the conflict is elminated by the preferred form of my invention, whichprovides seal supporting means l8, peripherally spaced about to feet,and intermediate seal loading or pusher means to urge the seal ringtowards the shell, peripherally spaced about 3 to 5 feet.

Moreover my improved seal supporting and guiding mechanism l9 may serveas additional seal loading means. The reverse, however, does not apply;I have found it is much more expensive to adapt pusher members 20 toserve as seal guiding and supportingmeans.

I show-each of the shoes l4-'A etc. suspended from the floating roof 12by one supporting and guiding means or hanger mechanism, generallydesignated by the numeral l9. Each .of these hanger mechanisms comprisesa roller track 2E,

vertically upstanding from the top of the floating roof I2;' a swinginglinkage member 22, pivoted to a lower part of the roller track andextending upwardly and outwardly therefrom; and a connecting linkagemember 23, having one end pivoted to an upper part of a seal shoe suchas MA, the other end equipped with atroller 24 on roller track 2], andan intermediate point pivoted to the free end of the swinging linkagemember 22. In this manner the linkage members form a toggle 22, 23, themovements of which are controlled by the track 2|, floating roof l2 ingroof I2; it being desirable for the linkage member 23 to be as short aspossible and to form a rather acute angledefinitely less than 45degrees-with the roller track, in order to prevent binding of the roller24 and other difflculties. Thus the room occupied by the mechanisms l8,radially of the tank, is insignificant, facilitating access to all partsof the roof and gam - 4 3 ft. high, wherebyfor inspectionandmaintenance. The linkage members 22 and the roller 2 is forced tomove in a straight line along the track 2|. Thus the outer end of thelink 23 is also forced'to move in a straight line relative-tothe'floating roof.

In order to keepthis line horizontal I make the connecting linkagemember 23 twice as long as the swinging linkage member 22, I pivotthetwo linkage members together in the middle of the connecting linkagemember 23, and I install the track 2! perpendicularly to the floatingroof l2; said roof, of course, being horizontally supported by and uponthe horizontal liquid level 13. Upon reference to Fig. 5 it will beunderstood that the end points of the linkage members 22 and 23 form thecorners of a triangle ABC. The joint between the two linkage members ispoint 1). Thus I have two isosceles triangles ABD and BBC, having sideBD and vertexnincommon; sidesADandDCforminga straight line ADC. Theimportant point is that, regardless of the angle BAG which obviously canvary, ABC always is a right angle. Accordingly side AB always ishorizontal, side BC being vertical.

The proof of the proposition that ABC is a right angle is readily foundupon construction of auxiliary lines DE and DF through vertex D,perpendicular respectively to bases BC and AB. Since ABD is an isoscelestriangle the line DF, being perpendicular to the base by construction,bisects the vertex angle ADB. Similarly the line DE bisects the vertexangle BDC. This is true regardless of the magnitude of each of saidangles. The two vertex angles total 180 degrees since ADC is a straightline. Accordingly the angle FDE between the two bisectors DF and DE is aright angle. The quadrangle FDEB, then, has right anglm at F and E byconstruction, and at D according to the above. Thus the fourth angle FBEor ABC must be a right angle also, as was to be shown.

In other words, if the float roof changes its position on the liquidlevel B, for instance if the wind forces it from position l2 to I2shifting point B to B linkage member 23 can freely rotate around pointA, shifting point C to C no uncontrolled forces are applied to seal ringll incident to this process, either upwardly or downwardly, andundesirable distortion of the seal ring isavoided. It is safely avoidedeven in the event that the ring, with clamping memher I! for fabric I,has considerable flexibility inordertoadapt itselftothetankwall l5irrespective of local obstructions.

Thesealguideandhanger l9 canbeadapted to urge the seal ring ll towardsthe shell l5, by means of a loading device shown in form of a tensionspring 25. This spring has one end attached to the axle of the roller 2|and the other end attached to a lower part of the roller track 2|. Inposition I2 when some parts of the floating roofare closertothe tankshell l5 than I whichis not absorbed by the track 2| and float seal.Themechanisms it will generallybeabout 15 member 23 and clamp ll. Atthis clamp, the

they are readilyaccessibie 2': are rigid, and

force so transmitted is dissolved'into two components; one tending tobend the top 01' the seal ring inwards ltnis must be IeSlSEcQ by thatamount or rigidity that provided in the seal ring, as previouslymentioned); and another, tending to press the seal ring against the sidewall l5.

'lhe magnitude of the spring force, and thus the magnitude or the forcestransmitted to the seal ring, increases as the noating roor approachesthe side wall; however the last-mentioned component, horizontallydirected against the side wail, decreases due to the increasing angleBAC. In some instances the spring 25 can be so selected, according tomechanical principles known to persons skilled in the art, that thedecrease of the horizontal component at A more or less compensates forthe increase in total magnitude of the spring force. From a practicalstandpoint, the ultimate eifect of the spring force resides in the totalhorizontal force between the floating roof l2 and the stationary wallI5, at each point of the periphery, transmitted at points A, B and C.The angularity at BCA and other points; together with the downward forceof spring 24,

can be selected so that this total horizontal v spreading force in eachmechanism I9, is more or less uniform regardless of a slightly excentricposition of the floating roof; or it can be selected so that itincreases in a predetermined manner upon a lateral shift of the floatingroof, thereby tending to keep the floating roof centered within thetank.

In this manner each of the seal shoes is suspended, horizontally guidedand positively urged against the tank shell by at least one hanger,guide and loading device IS; the floating roof is yieldingly centered inthe tank; and the seal ring is allowed to cling to the tank shellwithout distortion incident to required movements, and

from corrosion by the fabric IS; without this,

fabric, corrosive vapors would rapidly impair their action, at least insome instances. Of course the devices l9, preferably, are also protectedfrom atmospheric corrosion, by galvanizing or the like.

As mentioned before, I also provide seal loading or pusher members,generally shown by numeral 20. Each of these pusher members comprises ahorizontal pipe 26 rigidly secured to and spaced above the top of thefloating roof l2 by a post 21, radially of the root and tank; a pipe orbar 28 of smaller diameter inserted in and preferably extending throughthe pipe 26 and secured to the top of the seal shoe I4; a compressionspring member 29 engaging an inher end of the pipe 26 and an outer endof the pipe 28 so as to push the latter and the seal against the tankshell; and conventional spring abutment means (not shown in detail) toprovide this engagement. The pusher members occupy some space, radiallyof the tank, but they are generally only about 1 ft. high so that theypresent no serious obstruction; the seal ring and the other mechanismsare still accessible without diiiiculty.

It will now be seen why the members I 9 cannot bers 20. The latter wouldbe unable to perform the necessary guiding and suspending functions; thecompression springs would be jammed between the pipes 28 and 28, and thedevice would become inoperative upon any upward or downward movement ofthe roof. It is true that certain forms of pusher members are knownwhich are capable of performing several or all of these three functions.However such devices are much more complicated, expensive and cumbersomethan the simple pusher members 20 hereof, or the combination of thelatter with the members l9; they are harder of access and maintenance.

and they make it much more difficult to provide necessary access to theseal shoes, fabric, and clamping devices.

Various modifications may occur to persons skilled in the art.

I claim:

1. In a storage tank for volatile liquid, a floatmg roof; asubstantially cylindrical seal ring disposed around and spaced from thefloating roof, contacting the wall of the tank and extending from aboveto belowthe liquid level; a seal fabric connecting an upper part of theseal ring with. an upper part of the floating roof; hanger and guidemechanisms for the seal ring, distributed around the periphery of thefloating roof, each of said mechanisms comprising a roller track,vertically upstanding from the top of the floating roof; a swinginglinkage member, pivoted to a lower part of the roller track andextending upwardly and outwardly therefrom; and a connecting linkagemember twice as long as the swinging linkage member, having one endpivoted to an upper part of the seal ring, the other end equipped with aroller. on the roller track, and the point in the center between saidends pivoted to the free end of the swinging linkage member.

2. Apparatus according to claim 1, additionally comprising loading meansto urge the roller downwardly along the roller track and thereby to urgeat least parts of the seal ring outwards.

3. Apparatus according to claim 2 wherein said additional. meansconsists of a tension spring engaging the roller and a lower part of theroller track.

4. Apparatus according to claim 2 wherein the hanger and guidemechanisms and loading means are adapted to urge only spaced parts ofthe seal ring outwards; the apparatus additionally comprising pushermechanisms distributed around the periphery of the floating roof,between the hanger and guide mechanisms, and adapted to urgeintermediateparts of the seal ring outwards.

LESTER ANDERSON WILKINI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Laird Oct. 30, 1945

